Traffic signal



Jan. 18, 1955 R. F. STEHLIK 2,700,145

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Filed April 21, 1951 N RED [R J'I I02 A [RETURN 1 u i s INVENTOR.RUDOLPH F STEHLIK ATTORNEY United States Patent TRAFFIC SIGNAL RudolphFrank Stehlik, Antwerp, Belgium, assignor to Automatic ElectricLaboratories, Inc., Chicago, III., a corporation of Delaware ApplicationApril 21, 1951, Serial No. 222,173

9 Claims. (Cl. 340-46) This invention relates to traffic signal systemsin general, and more particularly to protective systems controlling theoperation of the various signals.

In such signalling systems heretofore used, upon failure of one signallamp in a group of signal lamps, a false indication might be given tothe controlled traffic during the critical period of changing thesignals. This indication then would deceive one direction of traifiewhile indicating properly to the cross directional traflic. Vehicleoperators in the one direction relying upon the usual dependability oftraiiic signals are then subjected to the possibility of collision withthe cross directional trafiic. The best interests of safety andmunicipal tratli c regulation require that such dangers be reduced to aTllllllmum.

Prior systems have been utilized including flashing signals, soundwarnings or complete disabling of the entire control system. Thesesystems do not solve the problem, but merely warn against it, orindicate a malfunctioning in some manner. The operator is apt to becomeconfused by this type of warning and the usual result is a controlsystem as unsafe as or more unsafe than continued operation of thesystem with the faulty lamp might be.

The present invention overcomes the disadvantages mentioned and providessafe control of traffic under circumstances of failure.

The object of my invention therefore is to provide for vehicle controlat a given trafiic intersection whereby a failure of one signal lamp ina signal unit will disable the other lamp in the same unit to prevent afalse indication during the critical signal change period for thatsignal unit.

This invention is applied to a system which provides only two lamps inthe traffic signal system. Both of the lamps are simultaneouslyilluminated to indicate the can-- tion period. In case the red lampbecomes defective. means are operative to partially disable the signalsystem by giving a dark signal during the caution period. Thus the greenlamp, under such circumstances, does not lllllmlnate during the cautionperiod in order to avo1d a false indication, and yet it operates asusual during the go period.

One feature of my invention whereby the desired re sults are obtained isa novel relay combination for con trolling the signal circuits uponfailure of one circuit therein.

A further feature is the novel interlocking arrangement used in therelay assembly to achieve the desired result.

Referring now to the illustration of my invention, which in thepreferred embodiment involves a Z-lamp signal unit, although theinvention may be adapted easily to a 3-larnp system; i

Figure 1 shows the schematic circuit arrangement for a given signal unitshowing two separate relays.

Figure 2 is a plan view of a modified form of relay structure showing aninterlocking arrangement for the two relays of Fig. 1.

Figure 3 is a front view of Figure 2 showing the armature interlockingarrangement.

Figure 4 is a view along line AA of Figure 2 showing the springarrangement.

Figure 5 is a side view of Figure 2 showing the spring arrangement andthe structure suitably enclosed.

Figure 6 is a circuit arrangement showing the circuit of Fig. 1 adaptedfor use with the modified relay of Fig. 2.

In general the system operates in the following manner. In normaloperating conditions at a usual traific intersection of two streets foursets of signal lamps are visible, one to each of the four directions oftraffic. However, operation is similar at any number of intersectingstreets or any number of signal units. The controller, not shown,associated with the intersection controls the sequence and timing of thesignals. This controller is any well known means for controlling trafiicsignal systems of the Z-lamp type as herein described. In a twolightsystem, only red and green signals are used, and will indicate thosecolors to the intersecting traflic. The period of change from green tored and red to green requires a caution signal to slow the movingtraffic and alert the stationary trafiic. In such a system illuminationof the red and green lamps simultaneously in all directions is the usualcaution signal. However, such a signal to the moving traffic only mayalso be used. It is then apparent that failure of the red lamp would becritical, for then the simultaneous signal of both lamps would notappear in the defective unit. In this situation a relay operates toremove the green lamp from the circuit during the warning or cautionperiod and a darkened signal appears to the moving traffic. This willindicate malfunctioning of the signal and slow the moving traffic which,upon observing the cross-directional traffic alert signal andsubsequently the go signal to that traflic, will stop. At the nextchange period the darkened signal will remain so during the change orcaution period and at the proper time, the green lamp will indicate asthough the signal were in proper working order.

The green lamp in the above description is removed from the circuit inthe defective signal unit in a manner hereinafter described in detailwith reference to the figures illustrating the preferred embodiment ofmy invention.

Figure 1 shows schematically the structure desired to perform in therequired manner. Relay A is connected in series with the red lamp R sothat its operation will be dependent upon a complete circuit throughthat lamp. Armature A2 is placed to operate responsive to the encrgization and deenergization of coil A and when operated completes acircuit from battery at the controller, over lead 101, through contactA, armature A2, green lamp G, to ground at the controller. Thus thegreen and red lamps may operate simultaneously with battery potentialplaced upon the incoming leads 101 and 102 by the controller.

Another coil B, is connected in parallel with the red lamp and anarmature B2 is provided therefor which will open a circuit to the greenlamp G when this coil is energized.

The sequence of operation in detail is as follows. Bat tery potential isreceived over lead 102 from the controller (not shown), through relay A,through lamp R, to common ground lead 100. A energizes, closing A2 andA1, and lamp R illuminates. Relay B also energizes at the same timesince it is directly across leads 102 and 100, but is slow to operatearmature B2, hence A2 operates first. After a predetermined intervalbattery potential is placed on lead 101, through Al, and A2 to lamp G,to common ground lead 100. Lamp G now illuminates. Simultaneous lightingof both lamps gives the caution signal. Battery potential is thenremoved from 102 after a timed interval, relay A and B dcenergize andlamp R darkens. Armature A2 is slower to release than 132. and when B2falls back, lamp G remains illuminated over a path from battery at thecontroller, lead 101, contact B1, armature B2 through lamp G to groundat 100. The signal now indicates go to the traffic it controls.

This period ends at a predetermined interval and the change back to thestop condition commences by battery potential being received over lead102 again, from the controller through the winding of series relay Athrough the filament of lamp R to ground over lead 100. Both lamps arenow illuminated, as a caution" signal to slow the traflic. Relays A andB are energized, A again operating first. Battery is removed from 101 bythe controller and the lamp G darkens.

Assuming now that the lamp R is defective the following is the sequenceof operation.

Battery is applied upon lead 102 by the controller, but since lamp R isopen, relay A does not energize, but relay B does energize since it isdirectly across the pair of leads 102 and common ground 100. Armature B2operates opening the circuit 101 to ground through lamp G at contact B1.When battery is placed on 101 simultaneously with battery on 102 by thenext operation of the controller, lamp G will not illuminate due to theopen circuit at B1. When battery is removed from 102 only, relay Bdeenergizes, B2 falls back and a circuit is now completed from batteryon 101 through contact B1, armature B2 through lamp G to ground on 100.Lamp G now illuminates and functions as at normal. When battery is againplaced on 102 during the normal caution period, relay B reoperates andopens the circuit to lamp G. Thus lamp G never illuminates during thecaution period if lamp R is defective.

Referring now to Figures 2, 3, 4 and 5 the detail structure of thepreferred interlocking relay combination used to control the abovedescribed circuit is as follows, although any suitable interlockingstructure can be used.

A base 3 is suitably insulated by insulation 2 and is suitably enclosedby a casing 1 which has mounted thereon suitable terminal blocks forelectrical connections. mounted by means of heel pieces and 16respectively to base member 3 and suitably insulated therefrom.Armatures 13 and 14 are pivotally mounted upon heel pieces 15 and 16respectively in opposing directions. Armatures 14 and 13 have attachedthereto lever arms and 22, respectively. Lever arm 20 has mountedtherein, at the lower extreme end, a pin 21, which engages a suitablegroove or notch existing in lever arm 22. Individual to armature 13 isarmature arm 17 which extends into an operative position with respect tosprings 9 and 6 suitably mounted upon base 3 and insulated therefrom, bysuitable material 4 and 5. In the present embodiment springs 9 and 6 areshown as twin contact springs with the contacts 7 and 8 normally closed.Spring 9 has a suitable opening therein to allow extension of a buffer12 fastened to spring 6 there through into an operative position withrespect to the armature arm 17.

The normal operation of the relay structure in association with thecircuit described above is as follows. Battery received by the relayfrom the controller will energize series coil 18 and parallel coil 19simultaneously but 18 is so arranged to operate armature 14 before 19operates armature 13. When series coil 18 is energized, armature 14 isattracted into engagement with armature adjusting stop 15 which may beany suitable adjusting device. Lever arm 20 moves in association witharmature 14 causing pin 21 to pivot about bearing 26. Since pin 21 is inengagement with notch 25, lever arm 22 will then pivot about bearing 23thus raising armature 13 away from parallel coil 19. The simultaneousenergization of coil 19 as described will have no effect upon armature13, since it is physically impossible for coil 19 to overcome theinfluence of coil 18 on armature 14. Since armature arm 17 is associatedonly with armature 13, the operation of armature 14 will not affect themovement thereof or of bufier arm 12 and springs 6 and 9, and will haveno effect upon the circuit associated therewith. Therefore energizationof parallel coil 19 while coil 18 is also energized, will not affect themovement of armature arm 17 and buffer 12 for the reason mentionedabove. Deenergization of the series coil 18 while parallel coil 19remains energized, will result in the release of armature 14. Thispermits armature 13 to return within the efiective field of coil 19, andit may now be attracted thereto. The operation of the armature 13 in theabove described manner will result in the engagement of armature arm 17and buffer arm 12, thereby opening twin contacts 7 and 8. The abovedescribed operation of armature 13 will occur only when the safetyfeature of this relay is required.

Referring now to Figure 6, the operation above described of the relaycombined in association with the circuit shown in Figure 1 is asfollows. Battery is received from the controller (not shown), over lead102 through lamp R to terminal block 203 through series relay 18 toanother terminal 200 to common ground lead 100. Since relay 18 isarranged to operate before relay 19, lamp R illuminates and series relay18 energizes. Parallel relay 19 is also energized at this time Seriescoil 18 and parallel coil 19 are suitably tit) over a path from batteryat 102, terminal 202, parallel coil 19, terminal 200 andaground at 100,but does not cause operation of armature 13 because of the priorenergization of relay 18 and the interlock structure. Battery is nowreceived simultaneously over leads 102 and 101 during the caution periodof the signal. These paths can be traced as follows: lead 101 throughlamp G to terminal 201 to spring 6, contacts 7 and 8, spring 9 toterminal 200 to common ground lead 100, and lead 102 over the prior pathdescribed above for lamp R alone. Lamps G and R are both illuminatedduring this period. Battery is now removed from lead 102 by thecontroller which opens the circuit to lamp R and coils 18 and 19. Lamp 6remains operated over the previously described path.

Assuming now lamp R is defective, the safety feature operation of therelay is as follows. Battery is placed on lead 102 by the controller toindicate the caution period, but since lamp R is open the path may betraced to the terminal block 202, through coil 19 to terminal 200 tocommon ground lead 100. Coil 19 is now energized while coil 18 isdeenergized due to the open circuit. Armature 13 will operate in thiscondition due to release armature 14, by relay 18 and opens contacts 7and 8 of springs 6 and 9, respectively. This opens the circuit to G andlamp G goes out thus avoiding a false signal to the viewer of thesignal, both lamps are now darkened. Battery is now removed from lead101, yet remaining on 102. This is the normal stop period but since R isdefective the signal remains darkened as during the caution perioddescribed above. Battery is now replaced on lead 101 by the controllerbut since relay 19 remains energized, and armature 13 is operated,contacts 7 and 8 remain open as before described and G does notilluminate. The controller now removes battery from lead 102, relay 19deenergizes, 13 falls back and makes springs 7 and 8, and since batteryremains on lead 101, the lamp G will now illuminate over its formerpath. The outward appearance of the signal with lamp G illuminated isthe same as it would be to the observer at this time in the cycle as itwould he were lamp R not defective.

What I claim and desire to be protected by Letters Patent is:

1. In a traffic signal system, a signal unit comprising a single redlamp and a single green lamp, a first circuit for said red lamp, asecond circuit for said green lamp, controller means including a sourceof current and said two circuits for simultaneously operating said twolamps to indicate a caution period and for sequentially and periodicallycontrolling said red lamp and said green lamp over their respectivecircuits to indicate stop and start periods respectively, thecombination of a safety relay individual to said unit, relay meanscontrolled by a defective red lamp for enabling said relay foroperation, circuit means effective by said enabling means for operatingsaid relay in response to an attempt to operate a defective red lamp,and means operated in response to the operation of said relay disablingsaid green lamp by opening said green lamp circuit to prevent itsillumination during the controlled caution period when said red andgreen lamps would normally illuminate simultaneously.

2. In a traffic signal system, a signal unit comprising a single redlamp and a single green lamp, a circuit for said red lamp, a circuit forsaid green lamp, controller means including a source of current and saidtwo circuits for simultaneously operating said two lamps to indicate acaution period and for sequentially and periodically controlling saidred lamp and said green lamp over their respective circuits to indicatestop and start periods respectively, a safety relay individual to saidsignal unit, means for operating said relay in response to a failure ofsaid red lamp during said caution period, and means operated in responseto the operation of said relay to extinguish said green lamp by openingsaid green lamp circuit during said caution period to provide a darkenedsignal unit during said caution period to warn said traific of thedefective condition of said signal.

3. In a traffic signal system, a signal unit comprising a single redlamp and a single green lamp, a circuit for said red lamp, a circuit forsaid green lamp, controller means including a source of current and saidtwo circuits for simultaneously operating said two lamps to indicate acaution period and for sequentially and periodically controlling saidred lamp and said green lamp over their respective circuits to indicatestop and start periods respectively, the combination therewith of asafety relay individual to said signal unit, means for operating saidrelay in connection with the illumination of said red lamp over said redlamp circuit during said stop and caution periods, interlocking means insaid relay operated in response to the operation of said relay toprevent further operation of said relay during said stop and cautionperiods, means in said relay for disabling said interlocking means incase said red lamp fails during said stop and caution periods, and meansoperated in response to the disabling of said interlocking means todisable said green lamp circuit to prevent operation of said green lampduring the normal caution period.

4. In a traflic signal system, a signal unit comprising a single redlamp and a single green lamp, a first circuit for said red lamp, asecond circuit for said green lamp, controller means including a sourceof current and said two circuits for simultaneously operating said twolamps to indicate a caution period and for sequentially and periodicallycontrolling said red lamp and said green lamp over their respectivecircuits to indicate stop and start periods respectively, thecombination therewith of a safety relay individual to said signal unit,interlocking means in said relay for controlling the sequence ofoperation of said green lamp over said green lamp circuit, relay meansoperated rendering said interlocking means inefiective in case said redlamp is defective during said stop and caution periods, and meansoperated in response to the operation of said relay means disabling saidgreen lamp circuit to prevent operation of said green lamp during saidcaution period.

5. In a traffic signal system, a signal unit comprising a single redlamp and a single green lamp, a first circuit for said red lamp, asecond circuit for said green lamp, controller means including a sourceof current and said two circuits for simultaneously operating said twolamps to indicate a caution period and for sequentially and periodicallycontrolling said red lamp and said green lamp over their respectivecircuits to indicate stop and start period respectively, the combinationtherewith of two relays, means for operatively interconnecting said tworelays to prevent complete operation of one when the other is operated,means for energizing both of said relays in connection with said redlamp and for operating only said other relay, means for releasing theother and completely operating the one of said relays upon failure ofsaid red lamp, said interconnecting means being rendered inetfectiveupon said release of said other relay to permit complete operation ofthe one of said two relays, and means operated in response to thecomplete operation of the one of said two relays for preventing theoperation of said green lamp while said one relay remains operated toprevent a false signal showing during the caution period.

6. In a traffic signal system, a signal unit comprising a single redlamp and a single green lamp, a first circuit for said red lamp, asecond circuit for said green lamp, controller means including a sourceof current and said two circuits for simultaneously operating said twolamps to indicate a caution period and for sequentially and periodicallycontrolling said red lamp and said green lamp over their respectivecircuits to indicate stop and start periods respectively, thecombination of a safety relay included in said red lamp circuit, saidred lamp circuit rendering said relay inoperative in case said red lampbecomes defective during its caution and stop periods, means for openingsaid second circuit to prevent illumination of said green lamp duringthe caution period, and means for controlling said last mentioned meansonly in case said relay is rendered inoperative.

7. In a tralfic signal system, a signal unit comprising a single redlamp and a single green lamp, a red lamp circuit for said red lamp, agreen lamp circuit for said green lamp, controller means including asource of current and said two circuits for simultaneously operatingsaid two lamps to indicate a caution period and for sequentially andperiodically controlling said red lamp and said green lamp over theirrespective circuits to indicate stop and start periods respectively, thecombination of a safety relay individual to said unit, means foroperating said relay over said red lamp circuit in connection with thecontrolled illumination of said red lamp during said stop and cautionperiods, means operated in response to the operation of said relay forpreparing said green lamp circuit for the controlled illumination ofsaid green lamp, means including said red lamp circuit for renderingsaid relay inoperative in case said red lamp becomes defective, andmeans operative during sai caution period in case said relay is renderedinoperative by a defective red lamp for disabling said green lampcircuit to prevent illumination of said green lamp during the cautionperiod.

8. In a tratfic signal system, a signal unit comprising a single redlamp and a single green lamp, a circuit for said red lamp, a circuit forsaid green lamp, controller terms including a source of current and saidtwo circuits for simultaneously operating said two lamps to indicate acaution period and for sequentially and periodically controlling saidred lamp and said green lamp over their respective circuits to indicatestop and start periods respectively, the combination therewith of twointerlocking relays, one of said relay series connected in said red lampcircuit to said red lamp, the other said relay connected to said redlamp circuit and connected in shunt of said red lamp, means foroperating said shunt relay in case said red lamp is defective duringsaid caution and stop periods, means controlled by said shunt relay fordisabling said green lamp circuit upon failure of said red lamp duringsaid caution period, and said green lamp being operated over said greenlamp circuit only during said start period.

9. In a trafiic system having stop, go, and caution periods, a firstrelay, a second relay, a stop circuit, a go circuit, means forcompleting said stop circuit during said stop period, for completingsaid go circuit during said go period, and for completing both saidcircuits during said caution period, means for operating said firstrelay over said stop circuit during said stop and caution periods, meansfor energizing said second relay over one portion of said stop circuitduring said stop and caution periods, mechanical means operated inresponse to the operation of said first relay for physically preventingsaid second relay from operating while said first relay is operated andsaid second relay is energized, said mechanical means being inetfectivein case said first relay releases, means for releasing said first relayduring said caution period in case another portion of said stop circuitbecomes defective, means for completely operating said second relay oversaid one portion of said stop circuit in case said first relay isreleased during said caution period, and circuit means operated by thecomplete operation of said second relay for disabling said go circuitonly during said caution period.

References Cited in the file of this patent UNITED STATES PATENTS1,900,723 Miller Mar. 7, 1933 2,065,815 Levy Dec. 29, 1936 2,100,313FitzGerald Nov. 30, 1937 2,166,721 Jetfers July 18, 1939 2,407,355 WellsSept. 10, 1946 2,491,891 Hopkinson, Ir Dec. 20, 1949 2,505,849 Bevis etal. May 2, 1950

